Optical disk apparatus and method for controlling movement of light spot thereof

Abstract

The method of the present invention comprises detecting a recording pattern, which is different for each tract, in each of track groups consisting of a predetermined number N or tracks recorded in advance on an optical disk(1), generating a tracking signal S ET whose signal level changes on the positive and negative sides of a target track T 0 as the center, and moving the optical spot to the target track T 0 on the basis of this tracking signal S ET . In this manner, it becomes possible to prevent uncontrollable movement of the optical spot and align the optical spot to a desired recording track within a short period of time.

What is claimed is: 
     
       1. An optical disk apparatus comprising an optical disk having a plurality of track groups, each with N tracks, on which recording patterns are recorded in advance, which patterns are different for each track in each said group of tracks, light spot scanning means, record track detection means for detecting said recording patterns for detecting the record tracks traversed by said light spot, tracking signal generating means connected to said record track detection means and responsive thereto for generating tracking signals which change in signal polarity on opposite sides of a target track, and which increase in level as said target track is approached, and light spot scanning means for moving the light spot as far as the target track on the basis of said tracking signals. 
     
     
       2. The optical disk apparatus according to claim 1, including discriminating means for determining that the difference in the number of tracks between the record track scanned by said light spot scanning means and the target track has become equal to or less than one half the prescribed number of tracks N constituting the group of tracks, to determine that said target track is being approached, and means for connecting said light spot scanning means to said discriminating means. 
     
     
       3. The optical disk apparatus according to claim 1 characterized in that said record track detection means causes a tracking error signal to be supplied to said light spot scanning means when the light spot reaches the target track. 
     
     
       4. The optical disk apparatus according to claim 1, including an actuator for coarse position adjustment and wherein said light spot scanning means comprises fine adjustment actuating means. 
     
     
       5. The optical disk apparatus according to claim 4, including means for driving said actuator in accordance with a function of the difference in the number of tracks between the record track scanned by the light spot and the target track. 
     
     
       6. A method for controlling the movement of a light spot in an optical disk apparatus in which an optical disk has plural groups of tracks, each with N record tracks having recording patterns thereon, comprising the steps of detecting record tracks traversed by the light spot by detecting the recording patterns previously formed on an optical disk, said recording patterns being different for each track in each said group of tracks, generating tracking signals changed in signal polarity on opposite sides of a target track, and increased in level as said target track is approached, and moving said light spot to the target track on the basis of said tracking signals. 
     
     
       7. The method for controlling the movement of a light spot in an optical disk apparatus according to claim 6, including the steps of discriminating that the difference in the number of tracks between the record track scanned by the light spot and the target track has become equal to one half of the predetermined number N, to determine that said target track is being approached, and switching the amount of controlled movement of the light spot based on the tracking signals in dependence upon the results of said discrimination.